X-ray generator mount



June 30, 1959 R. M. 'EMANUELSON 2,392,947

X-RAY GENERATOR MOUNT Filed Aug. 31, 1955 2 Sheets-Sheet 1 V 1/ A .4 :G

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Juhe 30, 1959 R. M. EMANUELSON 2,392,947

X-RAY GENERATOR MOUNT Filed Aug. 31, 1955 2 Sheets-Sheet 2 il w//////I/III Unitcd States Patet 2,892,947 Patented June 30, 1959 X-RAYGENERATOR MOUNT Roy M. Emanuelson, Woburn, Mass, assignor to HighVoltage Engineering Corporation, Cambridge, Mass, a corporation ofMassachusetts Application August 31, 1955, Serial No. 531,785

3 Claims. (Cl. 25091) This invention relates to apparatus for supportinghighvoltage X-ray generators, and in particular to a mount for heavyX-ray generators, such as those used in supervoltage therapy andindustrial radiography, adapted to provide vertical movement of suchheavy X-ray generators with minimum power, maximum safety, and a minimumamount of heavy machinery.

In accordance with the invention, power requirements are minimized byproviding the equivalent of a counterweight, wherein the downward forceexerted by the heavy X-ray generator is opposed by the upward force of ahydraulic or pneumatic ram, one end of which is connected to the X-raygenerator and the other end of which is mounted in some fixed position.The hydraulic or pneumatic ram derives its upward force from gas underpressure provided by a gas reservoir.

The source of motive power which imparts the desired vertical movementto the X-ray generator is a leadscrew system comprising a lead-screw anda gear motor mounted in a fixed position and a lead-screw nut attachedto the X-ray generator. When the lead-screw is rotated by the gearmotor, the X-ray generator is lifted or lowered; but the. actual forcethat the lead-screw system has to work. against is very small, since itis the difference between the force of the Xray generator exerteddownward and the force of the hydraulic or pneumatic ram system exertedupward.

Safety is provided by-virtue of the fact that the leadscrew systemby'itself is capable of supporting the X-ray generator, in the event ofgas pressure failure, in any position.

The use of a hydraulic or pneumatic ram system avoids the heavymachinery required with ordinary counterweights or with such mechanicaldevices as would be required to lift the X-ray generator with nocounterweight or its equivalent. By thus making possible the use ofsmall cylinders, pistons, motors, and other such components, theinvention avoids the use of bulky apparatus.

The invention may best be understood from the following detaileddescription thereof, having reference to the accompanying drawings, inwhich:

Fig. 1 is a diagram illustrating the principles of the invention, andshowing the use of a pneumatic ram;

Fig. 2 is a diagram similar to that of Fig. 1, but showing the use of ahydraulic ram in conjunction with a hydraulic accumulator; and

Fig. 3 is an isometric projection showing an X-ray generator supportedon an overhead mount constructed in accordance with the invention.

Referring to the drawings, and first to Fig. 1 thereof, a pneumatic ram1 comprising a piston 2 and a cylinder 3 is connected to a heavy X-raygenerator 4 in such a way that the downward force of the generator 4tends to push the piston 2 into the cylinder 3. Gas under pressure isfed into the cylinder 3 from a gas reservoir 5 via a suitable length oftubing 6, so that the gas under pressure exerts an upward force on thepiston 2 which opposes the downward force exerted by the weight of thegenerator 4. The total volume of the gas enclosure, which includes thegas reservoir 5, the tubing 6 and part of the cylinder 3, should belarge relative to the total displacement of the piston 2, so thatchanges in both volume and pressure are small as the piston 2 moves fromits collapsed to its extended position. The gas in the reservoir 5 iscontained under substantially constant pressure and consequently is notto be considered as the source of motive power which imparts verticalmovement to the X-ray generator 4.

The source of motive power is a lead-screw system comprising alead-screw 7 and a gear motor 8, which are mounted in a fixed position,and a lead-screw nut 9, which is attached to the X-ray generator 4.Operation of the gear motor 8 causes the lead-screw 7 to rotate, whichin turn imparts translational movement to the lead-screw nut 9, so as tomove the X-ray generator 4 vertically. However, owing to the action ofthe pneumatic ram 1, the actual work which must be done by thelead-screw system is very small, so that the size and power output ofthe gear motor 8 may be correspondingly small.

For practical reasons, it will generally be preferable to employ,instead of the pneumatic ram 1, a hydraulic ram whose cylindercommunicates with a suitable hydraulic accumulator upon which pressureis exerted by the gas from the reservoir 5. Such a modification is shownin Fig. 2, wherein a hydraulic ram 10, comprising a piston 11 and acylinder 12, is connected to the X-ray generator 4 in the same manner asthe pneumatic ram 1 of Fig. l. The piston 11 rests on a liquid, such asoil, which is fed into the cylinder 12 from a hydraulic accumulator 13via a length of tubing 14. The hydraulic accumulator 13 comprises anelastic membrane 15 compression of which moves the piston 11 upward andexpansion of which permits the piston 11 to move downward. The elasticmembrane 15 is enclosed in a chamber 16 into which gas is admitted fromthe gas reservoir 5 via a length of tubing 17. Since a liquid isvirtually incompressible, the pressure of the gas, which is exerted onthe outer surface of the elastic membrane 15, is transmitted into thecylinder 12 so as to provide the required upward force against thepiston 11.

It will be appreciated that various types of apparatus embodying theprinciples of the invention may be constructed without departing fromthe spirit and scope of the invention. However, for illustrativepurposes only, there is shown in Fig. 3 one embodiment of the inventionin which a heavy X-ray generator 4 is supported from the ceiling of theroom in which it is installed by means of an overhead mount constructedin accordance with the invention.

Referring to said Fig. 3, a frame 18 is attached securely to the ceilingin any suitable manner, so as to constitute a fixed support for the restof the apparatus. A carriage 119 is mounted in the frame 18 in such amanner that it is guided by and capable of horizontal movement withrespect to the frame 18. One pair of idler sprockets 2b is mounted onthe frame 18, and another pair of idler sprockets 21 is mounted on thecarriage 19. The X-ray generator 4 is suspended from the frame 18 by apair of roller chains 22, one end of each of which is attached to atrunnion 23 on the X-ray generator 4 and the other end of each of whichis attached to the frame 18. The pair of roller chains 22 pass over bothpairs of sprockets 2t 21 as shown, so that horizontal translationalmovement of the carriage 19 is always accompanied by a correspondingvertical translational movement of the X-ray generator 4. In theembodiment of the invention shown in Fig. 3, the X-ray generator 4always moves through a distance twice that through which the carriage 19moves. By using more or fewer sprockets, the ratio of vertical movementof the generator 4 to horizontal movement of the carriage 19 may beincreased or decreased. A set of telescoping tubular members 24surrounding each roller chain 22 between the frame 18 and the trunnion23 serve to prevent the X-ray generator 4 from swinging.

The cylinder 12 of the hydraulic ram 10 is mounted on the frame 18, andthe piston 11 of the hydraulic ram 10 is mounted on a cross-bar 2Saffixed to the carriage 19. The gear motor 8 is mounted on the frame 18,and is connected to the lead-screw 7 so as to be adapted to rotate thesame. The lead-screw nut 9 is mounted inside the cross-bar 25, so thatrotation of the lead-screw 7 by the gear motor 8 couses horizontaltranslational movement of the carriage 19 with corresponding verticaltranslational movement of the X-ray generator 4.

The cylinder 12 is connected to the liquid-containing part of thehydraulic accumulator 13 via a length of tubing 14, and the gas chamberof the hydraulic accumulator 13 is connected to the gas reservoir byanother length of tubing 17. The hydraulic accumulator 13 and the gasreservoir 5 may be installed at any readily accessible place, since thetubing 14 may be of extended length. The gear motor 8 may be controlledby a suitable switch mechanism 26, which is connected to the gear motor8 by suitable leads 27 of appropriate length.

By means of the invention, an X-ray generator weighing over 5,000 poundsmay be raised and lowered by a fractional horsepower motor, without theuse of heavy machinery or complex devices otherwise necessary to move aload of such magnitude. Moreover, the ability of the lead-screw systemto support the X-ray generator by itself ensures safe operation even inthe event of gas or liquid pressure failure. The weight of the X-raygenerator is supported entirely by the gas and liquid pressure, so thatthe only work which need be expended in raising or lowering the X-raygenerator is that necessary to overcome frictional forces and smallpressure changes.

Having thus described several embodiments of the invention, it is to beunderstood that although specific terms are employed, they are used in ageneric and descriptive sense and not for purposes of limitation, thescope of the invention being set forth by the following claims.

I claim:

1. A mount for heavy X-ray generators, such as those used insupervoltage therapy and industrial radiography,

adapted to provide vertical movement of such heavy X- ray generatorswith minimum power, maximum safety, and a minimum amount of heavymachinery, comprising in combination: a hydraulic ram having a cylinderand a piston adapted to slide snugly in said cylinder, a hydraulicaccumulator having two compartments, the first of which contains aliquid and is connected to said cylinder so as to form a liquid-tightenclosure of substantially constant volume, a gas reservoir connected tothe second compartment so as to form a chamber of variable volumecontaining a substantially constant quantity of gas under pressure; aheavy X-ray generator connected to said hydraulic ram in such a way thatthe weight of the X-ray generator exerts a force which tends to decreasethe volume of said chamber; and a source of motive power other than saidgas under pressure for imparting vertical movement to said X-raygenerator and capable of supporting the entire weight of said X-raygenerator, the volume of said chamber being sufficiently large so thatchanges in both volume and pressure are small during vertical movementsof said X-ray generator.

2. A mount according to claim 1, wherein said source of motive powercomprises a lead-screw and a lead-screw nut coacting therewith, saidlead-screw being rotatably mounted in a fixed position and saidlead-screw nut being connected to said X-ray generator in such a waythat translational movement of said lead-screw nut resulting fromrotation of said lead-screw results in vertical translational movementof said X-ray generator, and means for rotating said lead-screw.

3. A mount according to claim 1, wherein said gas reservoir contains gasat high pressure, whereby the size of said hydraulic ram may be reducedand wherein the first compartment of said hydraulic accumulator isconnected to said hydraulic ram via an extended length of tubing,whereby said hydraulic accumulator and said gas reservoir may beinstalled at any readily accessible place.

References Cited in the file of this patent UNITED STATES PATENTS2,623,361 Dungler Dec. 30, 1952 FOREIGN PATENTS 101,617 Sweden May 20,1951 535,984 Germany Oct. 17, 1931

